The problem you have is that relaxing of the laws has to happen gradually and simltaneously.

If one country or state or even town drops the drug laws, it gets overrun with the worst case scenario, as the very desperate flock to that region. The region then becomes a poster child for the 'I told you so's who will point at addicts, mess, and whatever external effects will come from that. If it is experimented and ends up in very public failure, the topic will be removed from discussion for a generation.

This is partially the case in Amsterdam, where most Dutch people wouldn't be seen in the red light district, as it is overrun with drug and sex tourists, usually from other countries. And do-gooders point to the Amsterdam red-light district and say 'see, do you want your town like that?', despite the fact that the laws are not Amsterdam specific, and apply to the country as a whole. And the rest of the country is a very pleasant place to be.

So you need to relax laws slowly and simultaneously, so that the problems can be dealt with as they arise, and successful health management can be introduced at the same time. And you have to take a very realistic view of the societal damage drug use can cause, no matter what type (ie beer or heroin).

Given these requirements, I can't see it ever happening in the foreseeable future, which pretty much guarantees the cartels will exist for a long time, possibly until they capture an entire nation and form an actual government.

EDIT: Just remembered a great line from the Ben Elton book (whose name I have forgotten) which is about removing drug laws.

The quote is something like : "Do you really care if another person becomes a heroin addict if it means your Grandma will not get mugged on the way home"

Really, it's all about people not trying to always rule and control the lives of others.